The visitors had early joy down the right when Javier Mascherano found Vidal in behind, but the winger's attempted cross was crucially cut out by Iraizoz.

Marc-Andre ter Stegen next produced a superb one-handed save low to his right to deny Douglas, while Suarez's inability to find a team-mate from a cut-back at the other end cost Barca a certain opener.

Valverde's side did not have to wait long for the breakthrough, though, and it came courtesy of a huge slice of fortune.

After Iraizoz kept out Messi's free-kick, the veteran keeper was left with no chance from the resultant corner as Alba's speculative volley took a heavy deflection off Benitez on its way into the bottom-left corner.

Barca began to take control by the half-hour mark and only an in-form Iraizoz prevented them from doubling their advantage, the 36-year-old quick off his line to smother another chance for Alba.

Paulinho and Michael Olunga still found time to exchange wayward headers as an entertaining first half ended with the away side ahead.

The lead became 2-0 almost immediately after the resumption when Vidal reached the by-line and attempted to find Suarez, who hurdled the back-heel pass and saw it trickle in via Iraizoz's legs.